Because of its advantages such as small size, inexpensiveness and noise-free operation, a so-called ink jet recording apparatus which is adapted to jet a liquid or molten solid ink through a nozzle, slit, porous film or the like against paper, cloth, film or the like to effect recording has been extensively studied. In particular, many monochromatic printers capable of recording on so-called ordinary paper such as report blank form and duplicating paper are commercially available. In recent years, printers capable of recording in all colors have been marketed.
An ink for use in these ink jet recording apparatus is mainly composed of a solvent, a coloring material and additives.
An ink for ink jet recording method has the following requirements:
(1) It must provide a high resolution, high density uniform image on paper without blurring or fogging; PA0 (2) When dried at the tip of the nozzle, it must cause no nozzle clogging, providing invariably good jetting response and stability; PA0 (3) It must be easily dried on paper; PA0 (4) It must provide an image with a good fastness; PA0 (5) It must have a good storage stability.
As an approach for obtaining a high density uniform image on ordinary paper there has been heretofore proposed the combined use of C. I. direct black 168 as a dye and thiodiglycol (JP-A-1-263169 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")). As an approach for improving the dryability of the ink on paper there has been proposed the addition of a surface active agent or polyvalent alcohol derivative (JP-B-60-34992 (the term "JP-B" as used herein means an "examined Japanese patent publication") and JP-B-62-13388). As an approach for preventing nozzle clogging there has been proposed the chelation of metallic ions with a chelating agent (JP-A-51-85804). In order to enhance the solubility of dyes, a method has been proposed which comprises the use of N-methyl-2-pyrrolidone, thiodiethanol, ethanolamine or the like as a solubilizing agent (JP-B-61-36876, JP-B-61-55546, JP-B-62-28828). Referring to jetting stability, it is thought that air dissolved in the ink foams, disturbing the jetting direction or disabling jetting. The addition of an oxygen absorbent has been proposed (JP-A-53-61412). Further, the addition of an anti-foaming agent has been proposed (JP-A-55-65268). Moreover, a method has been proposed which comprises the deaeration of the ink to inhibit foaming (JP-A-5-17712).
As mentioned above, many approaches for improving image uniformity, dryability on paper, anti-clogging properties and jetting stability have been proposed. However, none of these approaches can fully satisfy all the requirements.